Obtaining accurate position information for mobile stations, such as cellular or other wireless communication devices, is becoming prevalent in the communications industry. Satellite positioning systems (SPS's) such as, for example, the Global Positioning System (GPS) offers an approach to providing wireless position determination. An SPS user can derive precise navigation information including three-dimensional position, velocity and time of day through information gained from satellite vehicles (SVs) in orbit around the earth. The signals that are received from the SVs are typically rather weak. Therefore, in order to determine the position of the receiver, the receiver must be sufficiently sensitive to receive these weak signals and interpret the information that is represented by them.
One limitation of current SPS receivers is that their operation is limited to situations in which multiple satellites are clearly in view, without obstructions, and where a good quality antenna is properly positioned to receive such signals. SPS signals are severely attenuated in an indoor environment or other areas that suffer from blockage conditions, e.g., with significant foliage or urban canyons. Consequently, determining a position using SPS in environments with blockage conditions or generally weak signals is difficult.